But we forget the stars. If our descriptions have been carefully followed, the reader will now know the zodiacal constellations as well as those of the north. There remains but little to do to know the entire sky. But there is an indispensable addition to be made to what precedes. The circumpolar stars are perpetually visible above the London horizon; at any time of the year when we wish to observe them it is sufficient to turn to the north, and we shall always find them, either above the pole star or below it, to one side or the other, and always maintaining among themselves the relations which we have employed to find them. The stars of the zodiac do not resemble them from this point of view, for they are sometimes above the horizon, sometimes below. It is necessary, then, to know at what epoch they are visible. For this purpose it will be sufficient to remember the constellation which is found in the middle of the sky at _nine o’clock in the evening_ on the first day of each month—that, for example, which crosses at that moment a line descending from the zenith to the south. This line is the _meridian_, of which we have already spoken; all the stars cross it once a day, moving from east to west—that is to say, from left to right. In indicating each of the constellations which pass at the hour indicated, we also give the centre of the visible constellations. On January 1 Taurus passes the meridian at 9 o’clock in the evening; notice Aldebaran, the Pleiades. On February 1 the Twins (Gemini) are not yet there; we see them a little to the left. March 1, Castor and Pollux have passed; Procyon to the south, the little stars of the Crab (Cancer) to the left. April 1, the Lion, Regulus. May 1, β of the Lion, Berenice’s Hair. June 1, Spica of the Virgin, Arcturus. July 1, the Balance (Libra), the Scorpion. August 1, Antares, Ophiuchus. September 1, Sagittarius, Aquila. October 1, Capricornus, Aquarius. November 1, Pisces, Pegasus. December 1, Aries, the Ram. Our general review of the starry sky must now be completed by the stars of the southern heavens. Below Taurus and Gemini, to the south of the zodiac, you notice the giant Orion, who raises his club toward the forehead of the Bull. Seven brilliant stars are here distinguished; two of them, α and β, are of the first magnitude; the five others are of the second magnitude, α and γ mark the shoulders, κ the right knee, β the left knee; δ, ε, ζ mark the belt or girdle. Below this line is a luminous train of three stars, very near each other; this is the Sword. Between the western shoulder and Taurus is seen the Shield, composed of a row of small stars. The head is marked by a little star (λ) of the fourth magnitude.